Method and apparatus for exchanging heat



July 7, 1931. a. D. DODD METHOD AND APPARATUS FOR EXCHANGING HEAT Filed March 24. 1928 fer. In many cases' it is 0.30 In the accompanying tion as changes in .60 cure a two-stage Patented July 7, 1931 PATE NT OFFICE GERALD n. Dom), or oREENs'BURG, PENNSYLVANIA ME'rfron AND APPARATUS FOR, EXGI-IANGING HEAT Application filed Mama, 928. Serial No. 264,342.

' The present invention relates broadly to theart of heat exchanging, and more particularly to an improved method and apparatus by means of which the heat of a 5 high temperature liquid is more efiect vely transferred for heating a relatively low temperature liquid. V

In heat exchangers of the two surface type in which the transfer of heat is from 10 one liquid to another, the rate of heat transfer per square foot of surface per mean degree of temperature difference per hour 18 comparatively low even though special provision 18 made either for agitating one 0 16 the liquids, or for 1ncreas1ng its velocity.

Even with maximum agitation it is apparently .only possible in practice to secure about half the heat transfer that it is possible to obtain with a steam to water transdesired to effect the exchangeof heat from a relatively small quantity of comparatively hightemperature liquid to a relatively large quantity of com paratively low temperature liqui In ad 2 cordance with the present invention, I provide conditions such that an advantageous heat transfer takes place with the use of less surface area than is ordinarily required in present day practice.

drawings I have shown for purposes of illustration only, a preferred embodiment of the presentinvention, itbein understood that the draw,- ingsdo not define the limitsof my inventhe construction and operation disclosed therein may be made without departing either from'the spirit of the present invention or the scope of broader claims.

In the drawings Figure 1 is a side elevational v1ew, partly broken away, and lar elydiagrammatic, of oneform of heat exc anger 1n accordance with the present invention, and a Figure 2 is a transverse sectlonal view on the line IIII of Figure 1,-l0oking in the direction of thearrows. 1 V In carrying out the present invention I provide apparatusof such nature as to seheat transfer, this being obtained by the provision of a heat exchanger 2 in combination with a heat exchanger 8. These heat exchangers may comprise entirely separate units, positioned" in any desired manner, or, as illustrated in the drawings, may be mounted in superimposed relationship on opposite sides of a common header 4. p

For admitting water to 'be-heated to the apparatus, the header l may be provided with a water inlet 5 adapted to deliver the water to the tubes 6 of the first water pass. These tubes in turn discharge into a header f 7 constructed to direct the water into the tubes 8 of the second pass. The water then flows in succession, as indicated by the arrows, through the tube passes 9 and 10.

The last tube pass'in the heat exchanger 3 communicates through a: suitable passage way 11 in the header 4 with the tubes l2- constituting the first pass in the heat exchanger 2. From these tubes the water flows in succession, as indicated by the arrows, through the tube passes 13, 14: and 15. After leaving the tubes 15, the water may be discharged through the outlet connection 16. Y

The flow paths provided by the tubes may be considered as constituting thewater space of-the apparatus, and the space surround ing the tubes as constituting the heating space. Communicating with the heating space l7-of the heat exchanger 2 is an inlet connection 18 including a throttling valve 19, a suitable baffle QO' preferably being provided within the; heating space in cooperative relation to the discharge end of the coninto the apparatus through the inlet 5, and

there are 13,650 pounds of water at*"172.8 degrees being assed into the heating space i -17 per hour. ssuming the usual coefficients of heat transfer, the water. in passing through the tube passes 6, 8, 9 and 10 will fer of heat in the heat exchanger 2, thus providing an efficient heat interchange. Assuming the same conditions referred to, the amount of vapor released in the heat exchanger 2 would heat the water in the tube passes 12, 13, l l and 15 to a temperature of approximately 98.8 degrees. The operation of heating in the heat exchanger 2 will result in condensation of the vapor, which will collect in the bottom of the heat exchanger and pass through condensate passages 21 into the heating space 22 of the heat exchanger 3. The heating space of the exchanger 3 is preferably divided by a series of baffles 23 to provide a tortuous flow path for the condensate in order to effect a more intimate contact between the same and the tubes. This contact will result in increasing the temperature 'ofthe water to approximately 82.25 degrees as referred to, and will lower the temperature of the condensate to approximately 89 degrees, at which temperature itmay be withdrawn through the ofl'take 2 1.

In order to prevent the heating space 17 of the heat exchangers from becoming air bound, it may be provided with one'or more vents 25 connected with means for withdrawing such air from the 'spacel'r', as well understood in the art. The high. point in the water space, represented in the illus trated embodiment by the header 26, may likewise be provided with a specially constructed vent 27, by means of which any air or other gases may be withdrawn without withdrawing the water.

It will thus be apparent to those skilled in the art that I provide for an effective utilization of a comparatively small amount of high temperature liquid such as available in power plants in the form of drips, and effect a heat interchange under such conditions that the tube surface may be kept at a minimum and still insure the desired exchange of heat.

The construction further obviates the neoessity of high water velocities and the consequent high head losses encountered where such velocities are present.

Certain advantages of the present inven tion arise from the combination of a vapor to liquid heat transfer with a liquid to liquid heat transfer, the liquid to liquid heat transfer preferably occurring in the lower temperature ranges.

Still other advantages arise from the method of flashing a heating liquid to provide vapor for heating purposes, and thereafter collecting the condensed vapor and utilizing the condensate as a heating medium.

I claim 1. In a heat "exchange apparatus, a plurality of heat exchange units of the twosurface type, connections for passing comparatively cool water serially through said units, means for introducing comparatively high temperature water into one of said units and flashing the same therein, means for collecting condensate formed in said last mentioned unit and passing it to the other unit, and means providing a tortuous flow path for the condensate in said other unit.

2. In a heat exchange apparatus, a plurality of heat exchange units of the twosurface type, connections for passing relatively cool water through each of said units in one direction, means for introducing relatively hlgh temperature water into one of said unlts and causing it to flash therein,

means for passing the condensate from such unit into the other unit, and means in the second uni-t for producing a condensate flow opposite to the flow'of relatively cool water.

In a heat exchange apparatus, a plurality of heat exchange units of the twosurface type, each comprising a water space and a heating space, connections for passing water through the water space of said units, means for introducing relatively high temperature water to the heating space in one of said units, and

means for passing all of the condensate from said unit direct into a predetermined relatively restricted one only of the other unit.

4:. In the method of heating, the steps comprising passing the liquid to be heated in a confined path serially through a plurality of heaters, subjecting said fluid to the action of relatively high temperature vapor in one of said heaters, collecting the condensate, and then causing the same to flow through the other heater parallel to the ,path ofthe liquid to be heated but in the opposite direction.

5. In the method of heating, the steps comprising passing liquid to be heated in a confined path serially through a plurality of heaters, flashing liquid into vapor in one of said heaters, collecting the condensate formed by said vapor, passing it into the other heater, and withdrawing it "therefrom to maintain the pressure on the condensate below atmospheric pressure.

6. In a heat exchange apparatus, a plurality of multi-pass heat exchange unitsya'nd a header common to said units, said header having a plurality of'separate passages extending therethrough for conducting independent fluid streams from one unit to the other.

7. A water box for heat exchange units, having flow directing means adapted for cooperation with opposed heat exchange units, and having a plurality of separate passages extending therethrough for directing fluid from one heat exchange unit to another.

8. In a heat exchange apparatus, a water heater comprising a liquid to liquid transfer unit, and a vapor to liquid transfer unit,

means for passing the liquid to be heated serially through said units, and means adj acent the upper portion of the liquid to liquid unit for withdrawing the heating liquid therefrom.

9. In a method of heating a fluid by abprising admitting the liquid under reduced pressure to a heat exchange unit of the twosurface type to vaporize the same, collecting the condensate, passing the condensate through a second heat exchange unit of the two-surface type, withdrawing such condensate from the second unit to maintain the pressure in the heating chambers of the two units below atmospheric pressure, and passing the fluid to be heated first through the second mentioned unit and then through the first mentioned unit.

11. In a method of heating a fluid by ab stracting heat from a liquid, passing the fluid to be. heated along a confined path, and transferring heat thereto from the heating liquid in two stages, the second stage comprising the steps of permitting the heating liquid to vaporize and be cooled and recondensed by the fluid to be heated, and the first stage comprising the steps of cooling the condensate by the fluid to be heated and withdrawing the condensate to maintain I pressures in the two stages below atmospherlc pressure.

In testimony whereof I have hereunto set my hand.

GERALD D. DODD. 

